The present invention relates to corrosion resistant alloys, and more particularly, to the use of corrosion resistant alloys as fluid ends to prolong the life of a well service pump.
Well service pumps are often used to introduce treatment fluids in a wellbore. For example, well service pumps are often used in hydraulic fracturing to increase or restore the rate at which fluids such as water, oil, and gas can be produced even from low permeability reservoir rocks. Well service pumps can be used to pump fluids that are used to create and/or extend existing fractures. These fractures allow oil or gas to travel more easily from the rock pores, where the oil or gas is trapped, to the production well. By pumping a fracturing fluid into a wellbore at a rate sufficient to increase the downhole pressure to a value in excess of the fracture gradient of the formation rock, a crack in the formation is created and allows the fracturing fluid to enter and extend the crack farther into the formation.
Well service pumps are usually provided with fluid ends within which reciprocating plungers place fluids under pressure. Typically, the body of a fluid end is an aggregate of metal blocks fastened to provide access to internal components for servicing. Suitable examples of fluid ends are disclosed in U.S. Pat. Nos. 5,102,312 and 5,253,987, which are hereby incorporated by reference. However, the joints between the blocks and the supporting features for the valves tend to weaken the body of a fluid end, limiting its pressure rating, and making it susceptible to corrosion, leaks and cracks. Moreover, fluid ends are often exposed to salt solutions under high pressures which can also lead to corrosion.
As used herein, “corrosion” refers to the disintegration of material into its constituent atoms due to chemical reactions with its surroundings. Corrosion can significantly reduce the fatigue life of a fluid end. As used herein, “fatigue” refers to the progressive and localized structural damage that occurs when a material is subjected to cyclic loading. Due to corrosion, it is not unusual for the bodies of fluid ends to fail under load, significantly cutting short their useful lives.
Fluid ends that break down can cause numerous and significant problems in the oilfield. For example, it is often very costly to replace a fluid end, which can cost tens of thousands of dollars if not more. Fluid ends often weigh hundred of pounds and a hoist is usually required to lift and position the various portions of a fluid end body. Consequently, treatment is often halted and delayed while waiting for replacement equipment which, in turn, can further compound the cost burden of replacing failed fluid ends.